Cluster calculations of local vibrational mode frequencies of impurities in III-V semiconductors: applications to defect complexes involving C_Asin GaAs

Abstract

A direct method for calculating local vibrational mode (LVM) frequencies from defect complexes in zinc blende structure Semiconductors is discussed.Interatomic interactions are described hy an extension of the Keating model. Sets of force constants for eleven pure host crystals, including homopolar and Ill-V semiconductors, are found by fitting to available phonon dispersion relations. Simulations of isolated impurities in Ill-V hosts are reported and, from these, some trends are deduced for the changes in force constants needed for reproduction of experimental measurements. The use of the method in the interpretation of experimental results from defect complexes is illustrated by detailed calculations of (i) isotopic fine structures of the CA, line and CA.and (ii) line patterns associated with carbon in AI,Ga, _.As. lines in GaAs

Infrared absorption due to local vibrational modes of nitrogen in GaAs:N and GaAs-based dilute nitrides

“…For In y Ga 1−y As 1−x N x with 0 < y < 1, five different local arrangements ('molecules') are possible: Ga 4 N, InGa 3 N, In 2 Ga 2 N, In 3 GaN and In 4 N. Due to symmetry lowering from tetrahedral symmetry (T d ), actually nine different modes are expected for N As in InGaAsN alloys. The very similar case of C As in AlGaAs alloys has been investigated theoretically by Sangster et al [34] using cluster calculations. The general trend is that the LVM frequencies of the mixed configurations are distributed between the frequencies of the pure configurations.…”

Lattice Sites of Silicon Impurities in AlGaAs Grown by Liquid Phase Epitaxy

“…Nevertheless, the presence of one or more perturbed shallow donor lines should still be expected in illuminated samples. Since all the SiG a atoms would have four As nearest neighbours and vibrational amplitudes associated with LVMs normally involve only the impurity and its nearest neighbours [8], any changes in their vibrational frequencies would be small. A second possibility is that lines 1abelled 1-3 are due to Si atoms located in DX configurations with second nearest neighbours interactions with Al atoms.…”